1. Field of the Invention
The present invention relates to an apparatus for iteratively measuring a blood pressure of a living subject who is undergoing a blood-dialysis treatment.
2. Discussion of Related Art
When a patient is undergoing a blood-dialysis treatment, the dynamic condition of his or her circulatory system may largely change and accordingly his or her blood pressure may largely change. The measurement of blood pressure of the patient under the dialysis treatment is usually carried out by not an invasive method in which blood pressure (BP) values can be continuously measured but a so-called Korotkoff-sound-type or oscillometric-type automatic BP measuring apparatus in which a BP value or values are determined based on the change of Korotkoff sounds, or the change of respective amplitudes of heartbeat-synchronous pulses of pulse wave, detected during the change of pressing pressure of a pressing belt (e.g., a cuff) applied to a body portion of the patient. However, each of the conventional automatic BP measuring apparatuses can obtain a BP value or values, only at a predetermined BP-measurement period. Therefore, if the BP values of the patient under the dialysis treatment significantly largely change immediately after the measuring apparatus measures a BP value or values in one BP measuring operation, the apparatus cannot detect any significant changes (e.g., decreases) of the BP values of the patient, until the measuring apparatus performs the following BP measuring operation after the predetermined BP-measurement period, which may be considerably long. On the other hand, if the BP measuring apparatus measures, in the entire duration of the dialysis treatment, a BP value or values at a BP-measurement period which is so short as to be able to detect any abrupt change of the BP values of the patient, the frequency at which the pressing belt presses the body portion of the patient is increased as such, which leads to increasing the burden exerted to the patient and even producing congestion in the body portion, which, in turn, introduces errors into the BP values measured.
Meanwhile, a doctor or a nurse can estimate, from his or her experiences, a specific partial duration, in the entire duration of dialysis treatment, in which the BP values of the patient may largely decrease, i.e., the BP measuring operations should be performed at a short period. Therefore, it has been generally practiced that the doctor or nurse modifies the BP-measurement-start period to a shorter period at a time around the start of the specific partial duration, and returns the shorter period to the initial, longer period at the end of the specific partial duration. In addition, there is known an apparatus which can employ respective BP-measurement-start periods for a plurality of partial durations in the entire duration of dialysis treatment, such that one of the periods that corresponds to a specific partial duration in which BP values of a patient may largely decrease is shorter than the period or periods for the other partial duration or durations.
However, both of the above-described conventional manners of monitoring of BP values are not only cumbersome but also need to employ a long specific duration associated with a short BP-measurement-start period, so that any large decrease of the BP values may assuredly occur in the specific partial duration. This leads to increasing the burden exerted to the patient. Moreover, even in the above manners in which the long specific duration is employed, there are known many cases where the large decrease of BP values occurs in the other duration or durations, in the entire dialysis duration, than the long specific duration and cannot be detected so quickly.
It is therefore an object of the present invention to provide a blood-pressure measuring apparatus which can measure a blood pressure of a patient who is undergoing a blood-dialysis treatment and which can quickly detect a decrease of the blood pressure of the patient, without exerting large burden to the patient.
In the above-described background, the present inventors have performed extensive studies, and have found that a specific partial duration, in the entire duration of dialysis treatment, in which blood pressure may abruptly decrease occurs depending on individual patients and that if there is the specific partial duration in which the blood pressure abruptly decreases, the specific partial duration is just a limited duration in the entire dialysis duration.
The above object has been achieved by the present invention, which provides an apparatus for iteratively measuring a blood pressure of a living subject who is undergoing a blood-dialysis treatment, comprising an inflatable cuff which applies a pressing force to a body portion of the subject; a blood-pressure measuring device which measures a blood pressure of the subject by changing the pressing force of the cuff applied to the body portion of the subject; a starting means for starting the blood-pressure measuring device at a predetermined period in a dialysis duration in which the subject undergoes the blood-dialysis treatment, so that the blood-pressure measuring device iteratively measures a blood pressure of the subject at the predetermined period; a period memory device which stores, for a plurality of living subjects including the subject, a plurality of sets of predetermined periods each set of which comprises respective predetermined periods for a plurality of partial durations of the dialysis duration; an identifying means for identifying the subject; and a selecting means for selecting, from the sets of predetermined periods stored in the period memory device, the set of predetermined periods for the subject, so that the starting means starts, in each of the partial durations of the dialysis duration, the blood-pressure measuring device at a corresponding one of the predetermined periods of the selected set, and the blood-pressure measuring device iteratively measures a blood pressure of the subject in the each of the partial durations of the dialysis duration at the corresponding one of the predetermined periods of the selected set.
In the present BP measuring apparatus, the identifying means identifies the subject, the selecting means selects, from the sets of predetermined periods stored in the period memory device, the set of predetermined periods for the subject, the starting means starts, in each of the partial durations of the dialysis duration, the blood-pressure measuring device at a corresponding one of the predetermined periods of the selected set, and the blood-pressure measuring device iteratively measures a blood pressure of the subject in the each of the partial durations at the corresponding one of the predetermined periods. Thus, the dialysis duration can be divided into a plurality of partial durations including at least one specific partial duration in which the BP values of the living subject may largely decrease and which is associated with at least one predetermined period shorter than at least one predetermined period associated with at least one partial duration of the dialysis duration other than the specific partial duration. Therefore, the present apparatus can be easily operated for monitoring the BP values of each individual subject (e.g., patient), and quickly detecting any abrupt decrease of the BP values of the subject, and the length of the specific partial duration can be minimized. which leads to reducing the burden exerted to the subject during the dialysis treatment.
According to a preferred feature of the present invention, the blood-pressure measuring apparatus further comprises a detecting means for detecting a change of the blood pressure values iteratively measured by the blood-pressure measuring device; and a modifying means for modifying, when the detecting means detects the change of the blood pressure values at an elapsed time in a first one of the partial durations of the dialysis duration that is associated with a longer predetermined period than a predetermined period associated with at least one of a second partial duration preceding the first partial duration, and a third partial duration following the first partial duration, the set of predetermined periods selected by the selecting means for the subject, such that the modified set of periods comprises, for a predetermined partial duration including the elapsed time, a period shorter than the longer predetermined period, the modifying means storing, in the period memory device, the modified set of periods in place of the selected set of periods.
In this BP measuring apparatus, the detecting means detects a change of the BP values iteratively measured by the BP measuring device, and the modifying means modifies, when the detecting means detects the change of the BP values at an elapsed time in a first partial duration associated with a longer predetermined period than a predetermined period associated with at least one of a second partial duration preceding the first partial duration, and a third partial duration following the first partial duration, the set of predetermined periods selected by the selecting means for the subject, such that the modified set of periods includes, for a predetermined partial duration including the elapsed time, a period shorter than the longer predetermined period, and additionally stores, in the period memory device, the modified set of periods in place of the selected set of periods. Thus, the contents or data stored in the period memory device are automatically modified as the BP values of the subject are iteratively measured by the BP measuring device.
According to another preferred feature of the present invention, the blood-pressure measuring apparatus further comprises a blood-pressure memory device which stores, for the subject, the blood pressure values iteratively measured by the blood-pressure measuring device in the dialysis duration, and respective elapsed times, after a commencement of the dialysis duration, at which the blood pressure values are iteratively measured by the blood-pressure measuring device; and a modifying means for modifying, when the blood pressure values stored in the blood-pressure memory device in the dialysis duration for the subject comprise at least one blood pressure value lower than a reference value, the set of predetermined periods selected by the selecting means for the subject, such that the modified set of periods comprises, for at least one first predetermined partial duration including at least one elapsed time corresponding to the at least one blood pressure value, a first predetermined period shorter than a second predetermined period for at least one second partial duration of the dialysis duration other than the at least one first partial duration, the modifying means storing, in the period memory device, the modified set of periods in place of the selected set of periods.
In this BP measuring apparatus, the BP memory device stores, for the subject, the BP values iteratively measured by the BP measuring device in the dialysis duration, and respective elapsed times, after the commencement of the dialysis duration, at which the BP values are iteratively measured, and the modifying means modifies, when the BP values stored in the BP memory device in the dialysis duration for the subject include at least one BP value lower than a reference value, the set of predetermined periods selected by the selecting means for the subject, such that the modified set of periods includes, for at least one first predetermined partial duration including at least one elapsed time corresponding to the at least one blood pressure value, a first predetermined period shorter than a second predetermined period for at least one second partial duration of the dialysis duration other than the at least one first partial duration, and additionally stores, in the period memory device, the modified set of periods in place of the selected set of periods. Thus, the set of predetermined periods and the corresponding partial durations, for the subject, are automatically optimized and stored in the period memory device.